I'm a designer and this is my first post in this fine forum. I'm designing a custom airplane frame and I need of the knowledge of the v-twin expert members of the board .
In the plan of my project, installing an HD Evo type v-twin in an inverted position (upside-down, with the crankcase up and the cylinders down) would be more rational than a traditional configuration.
I know that the v-twins can be considered as a part of an aircraft radial engine, I know that the HD v-twin separated lubrication allows the inverted work. Of course, I also know that the history of aviation is rich of famous inverted v-engines or radial ones and that in the acrobatic aircraft the engines can work inverted for a while, but I don't know if a stock HD Evo v-twin, or a S&S bigger colleague (like the T124 for example) with fuel-injection system can work at the same and normally if mounted inverted without modifications.

If an inverted v-twin working is not possible without modifications, what modifications the v-twin would need of?

The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft. The Vee configuration generally reduces the overall engine length, height and weight compared to an equivalent inline configuration.V-twin engines have a single crankpin, which is shared by both connecting rods. The connecting rods may sit side-by-side with offset cylinders, or they may be "fork & blade" items with cylinders in the same plane without an offset.

The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft. The Vee configuration generally reduces the overall engine length, height and weight compared to an equivalent inline configuration.V-twin engines have a single crankpin, which is shared by both connecting rods. The connecting rods may sit side-by-side with offset cylinders, or they may be "fork & blade" items with cylinders in the same plane without an offset.